1. Field of the Invention
In general, the present invention relates to a computer-implemented method and apparatus for performing data fusion. In particular, when utilizing an active sensor, such as a radar, multiple radar tracks may be generated which represents the same physical object. The present invention relates to a computer-implemented method and apparatus for determining whether two or more radar tracks represent the same physical object.
2. Description of the Prior Art
There are several methods of integrating data from multiple radars into a single system track file. The type of radar integration that should be used is a function of the radar's performance, the environment, and whether or not the radars are colocated. Several conventional integration methods which have been used are:
1. Track selection: Generate a track with each radar, and choose one of the tracks as the system track. PA1 2. Average track: Generate a track with each radar and weight, according to the Kalman filter's covariance matrices, the individual tracks to form a system track. PA1 3. Augmented track: Generate a track with each radar, choose one of the tracks as the system track, and use selected detections from the other radars to update the system track. PA1 4. Detection-to-track: Use all radar detections to update the system track; tracks may or may not be initiated by using all detections from all radars.
A prior art detection-to-track system is illustrated in FIG. 1. Radars 12 and 14, which include corresponding automatic detectors, provide inputs to a sensor input and control unit 16 which includes individual detection processors 18, 20. Each detection processor 18, 20 provides an input to a detection file 22, 24. The outputs from the detection files 22, 24 feed a data association integration circuit 26 which performs correlation of the track data received from the detection files 22, 24 and performs track entry and track update and writes the resulting outputs to a track file 28.
Theoretically, the detection-to-track method of integration yields the best tracks because all of the available information is used. However, the detections must be weighted properly and care must be taken so that bad data does not corrupt good data.
There are many advantages of radar integration. Probably the most important is that it provides a common surveillance picture to all users so that decisions can be made more effectively. Radar integration also improves track continuity and tracking of maneuvering targets because of the higher effective data rate. Improvement in track initiation times is a function of the target distance. For instance, long-range targets are usually detected by only one radar so that little or no improvement in initiation time is achieved. However, there could be an appreciable reduction in the initiation time for pop-up targets. Finally, the general tracking performance is improved in an electronic countermeasures (ECM) environment because of the integration of radars in different frequency bands located at different positions, providing both spatial and frequency diversity.
The main advantage of integrating different radar sensors is to provide classification and/or identification information on radar tracks. In general, other sensors do not provide position data of an accuracy comparable with radar data. The sensors can also alert each other to conditions which can cause the mode of operation to be changed. For instance, a strong direction-finding (DF) bearing strobe on a noise (jammer) source or emitter which cannot be correlated with any radar track may cause the radar to use burnthrough, lower its detection thresholds, or change its initiation criterion in the sector containing the DF bearing strobe.
As set forth above, radar integration has many advantages. However, most of the prior art methods relate to how to integrate two tracks, once it has been determined that integration is required. However, none of these methods actually determine when two tracks should be integrated because they represent the same physical object.